The aim of the proposed studies is to gain a better understanding of the influence of the nerve upon "fast" extensor digitorum longus and "slow" soleus muscles of the rat and of the alterations which occur when such influence is suppressed and subsequently reestablished. Pharmacological, electrophysiological and ultrastructural investigations of the alterations which occur in the "fast" posterior latissimus dorsi and "slow" anterior latissimus dorsi muscles of chickens with inherited muscular dystrophy will also be undertaken. Intracellular, extracellular, voltage clamp and Nomarski interference optic techniques will be used. Objectives: 1) to investigate the effects of drugs which suppress axoplasmic flow, e.g. local anesthetics, antimitotic agents and protein synthesis inhibitors, on the properties of the muscle membrane; 2) to assess the role of electrical stimulation of muscle and nerve in the process of regeneration; 3) to establish the physiological and pharmacological characteristics of the fibrillation potentials which appear after denervation in "fast" and "slow" muscles and to determine if there is any relationship between these potentials and the absence of a putative trophic factor; 4) to investigate the effects of suppression of motor nerve activity by batrachotoxin and its analogs and 6- aminonicotinamide; 5) to provide quantitative information on the electrophysiology and ultrastructure of "fast" and "slow" innervated, denervated, and cross-innervated muscles of chickens with inherited muscular dystrophy; 6) to study the mechanism of the atrophy which occurs in the "fast" muscles of dystrophic chickens and its correlation with the partial suppression of sodium conductance and decrease in quantal release; 7) to continue our studies involving density of ACh receptors in normal, denervated and reinnervated muscles using Nomarski interference optics; 8) to analyze the effect of toxins such as batrachotoxin, tityustoxin and polyamines on the pre- and postsynaptic membranes of "fast" and "slow" muscles and isolate the macromolecules reacting with these toxins; 9) to reveal the mechanism of action and reactive sites of histrionicotoxin and atropine, their analogs and alpha-bungarotoxin on "fast" and "slow" mammalian skeletal muscles.